Voltage Stability Monitoring From a Transmission Bus PMU

This paper examines the problem of monitoring long-term voltage instability from a phasor measurement units installed at any transmission bus. It is shown that the well-known impedance matching condition on a radially connected load bus, as well as the local identification of voltage emergency situations (LIVES) method based on load tap changing transformers can be generalized into a New LIVES Index suitable for any transmission bus feeding a weak area of a system. Results on an IEEE voltage stability test system validate the dependability and security of the new index for the early detection of voltage instability. Moving average, as well as a new filtering method based on short-time Fourier transform are employed to reduce the effect of noise and short-term transients.